Electric motor brush spring

ABSTRACT

A brush holder having a fine pitch extension-like coil spring which is used flexurally as a brush spring and has integrally formed ends adapted for slidable retention in a slot-like track adjacent and parallel to the brush.

United States Patent Gaudry 51 May 30, 1972 [541 ELECTRIC MOTOR BRUSH SPRING [72] Inventor: Paul Emile Gaudry, 40 Ouimet Street,

Laval des Rapides, Quebec, Canada [22] Filed: Oct. 9, 1970 21 AppL No.: 79,511

[52] U.S. Cl ..267/179, 267/ 1 8O [51] Int. Cl ..F16f13/00 [58] Field of Search 310/247, 245, 246, 242, 241

[56] References Cited UNITED STATES PATENTS 1,462,925 12/1921 Wilburger ..267/179 2,254,566 9/1941 Cornell ..267/180 Avery ..267/180 Kaiser ..267/179 FOREIGN PATENTS OR APPLICATIONS 822,860 11/1952 Germany ..310/247 Primary Examiner.l. D. Miller Assistant Examiner-R. Skudy Att0rneyWil1iam S. Henry I ABSTRACT 1 Claim, 4 Drawlng Figures ELECTRIC MOTOR BRUSH SPRING BACKGROUND OF THE INVENTION The present invention relates to an electric motor brush holder and particularly to an improvement in the carbon brush holding and associated spring urging means used in fractional to low horsepower universal electric motors and the like.

In most electric motors of the fractional to low horsepower range, the brush springs which are used are more often than not compression springs; however, compression springs exhibit at least two disadvantages, the first and most obvious of which is the fact that such springs are not constant force springs and that, therefore, the force with which they act on the carbon brushes decreases as the length of each brush shortens. Brush holders are known in which constant force springs are used but it appears that the cost and complexity of these holders are such that the resulting motors are in a price class of their own and do not constitute an economic alternative for any motor wherein compression springs are used. A well known type of constant force springs which has been used is the so-called Negator spring.

A second and almost equally significant disadvantage of compression springs resides in the fact that such springs exhibit a strong tendency to becoming almost desperately entangled with one another, particularly when a large number of them are held in the same container from which to be individually sorted out. This disadvantage becomes a real problem in the chain line assembly of electrical motors as it necessitates that all compression springs be kept individually separated at all times.

SUMMARY OF THE INVENTION The present invention proposes to avoid the aforementioned disadvantages of compression type brush springs and to offer an economically acceptable alternative therefor.

In the brush holding arrangement of the present invention, the spring which is used is characteristically an extension spring which, instead of being utilized tensionally, is utilized in bending or lateral flexing. It is generally recognized that the compression forces between the ends of flexed extension springs are very nearly constant, i.e. there is no appreciable difference between these forces at various degrees of flexural deformation.

Brush holders of the invention are also advantageous in that they simplify the assembly of motors.

A better understanding of the invention will be derived from the following disclosure of a preferred embodiment, reference being made throughout to the accompanying drawing thereof wherein:

FIG. I is a fractional schematic perspective view of a commutator and brush holders assembly in accordance with the present invention;

FIG. 2 is a longitudinal axial plan cross-section of a brush holding assembly in accordance with the invention;

FIG. 3 is a plan view of a holder forming a part hereof; and

FIG. 4 is a plan view of a brush spring forming a part of the invention.

There are shown in FIG. 1 two brush assemblies A and B of the invention extending radially outward in a common axial plane of a rotor 6 centrally disposed between them. For the purpose of the illustration only, the mounting sheath or assembly 2 of brush assembly B has been sectioned and one half thereof removed to give a view of the relative disposition of parts therein. Each holder 2 has a bore 3 which extends longitudinally therein fully from one end to the other; the crosssectional profile of the bore 3 geometrically coinciding with the cross-sectional profile of brush 4, sufficient clearance being provided throughout to allow unrestricted passage of the latter through the former.

There is a longitudinally extending slotted track in each brush mounting sleeve 2; the slotted track 5 having closed far and near ends 7 and 8 respectively. The width of the track 5 corresponds to the diameter of the neck portion 9 integrally fonned in extension-like coil spring 10 and particularly at each end of the main body portion 1 1 thereof. There is formed at the outer end of neck portion 9 a terminal portion 12 in the form of a knob increasing in diameter from that of neck portion 9 to approximately that of body portion 11. Close to the far end 7, there is formed in the slotted track 5 a widened gap 13 for insertion therethrough of the knob-like terminal portions 12 of the extension-like coil spring 10. As is common with extension springs, adjacent turns of all portions of spring 10 are substantially in contact with each other when the spring is in relaxed condition, as is shown in FIG. 4. This precludes the possibility of the springs becoming entangled with each other during storage.

The knob-like terminal portions 12 are provided for preventing escape of the neck portions 9 from the slotted track 5 and, also to provide sufficient bearing surface against back end 14 of the brush 4 for transmission therethrough of the urging force from spring 10. The neck portion 9 integrally formed between the main body 11 and knob 12, being of a reduced diameter offers more resistance to bending. Consequently the bending value is established by the main body ll only.

The preferred material for the holder 2 being plastic, the electrical connection of brushes 4 may be realized through the provision of flexible shunt wires 15 formed integrally of the brush 4 and projecting from the back end thereof. The connection of the shunt wires 15 may be realized through the provision of appropriate connector means 16 for which a connector seating recess 17 may conveniently be provided at the outer end of the holder 2. The provision of a near end or bridge 8 terminally of the slotted track 5 is not absolutely necessary to the invention but it is preferred because a further advantage may be realized therethrough. Assuming that the length of the neck portion 9, the thickness of the material of sleeve 2, the distance of bridge 8 from the commutator C are all proportioned accordingly, it is seen from FIG. 2 that in the absence of a brush, bridge 8 prevents excessive inward extension of the spring 10, thereby avoiding injury to the commutator surface that would otherwise result from the rubbing action of one of the knoblike terminal portions 12 of the spring against the surface of the commutator C.

In the assembly of motors and generators, the installation of brushes 4 in brush holders of the invention is the last operation; the holders 2 are secured in position and brushes 4 are pushed in position therein; in each holder 2 a first terminal portion 12 of one extension-like coil spring 10 is pushed-in through the widened portion 13 of the slot-like track and as the neck portion 9 comes in line with the track 5 it is pushed longitudinally to engage it and thereby liberate the aperture widened portion l3; the spring 10 is bent or flexurally stressed to bring the second terminal portion 12 over the widened portion 13 of the track; the second terminal portion is then pushed through the widened portion 13 until the adjacent neck portion 9 thereof comes into engaging alignment with the track 5 whereupon the spring is released; as the spring 10 tends to straighten, the knob-shaped terminal portions 12 thereof will move longitudinally away from one another as far as possible, one terminal portion 12 bearing against the rear end 14 of the brush and the other terminal portion 12 bearing against the underside of the track's far end portion 7. Finally, the connection of the shunt wire 15 is made.

What is claimed is:

1. A spring comprising a single strand of wire, said spring having a coiled flexual central portion of given diameter, each end of said central portion terminating in a transition coil of said wire having a diminishing diameter until the minimum coil diameter of said spring is reached, each coil of said minimum diameter forming a neck portion extending coaxially with said central coil, each of said next portions terminating in a coil of said wire defining a knob having a diameter increasing from that of said minimum diameter, and adjacent turns of all portions of said spring being substantially in contact with each other when said spring is in relaxed condition.

Disclaimer 3,666,258.Paul Emile Gaudry, Laval Des Rapides, Quebec, Canada. ELEC- TRIC MOTOR BRUSH SPRING. Patent dated Ma 30, 1972.

Disclaimer filed Sept. 5, 1972, by the assignee, Console ated Foods Oarpomtz'on.

Hereby disclaims the entire term of said patent.

[Ofiiez'al Gazette October 3, 1972.] 

1. A spring comprising a single strand of wire, said spring having a coiled flexual central portion of given diameter, each end of said central portion terminating in a transition coil of said wire having a diminishing diameter until the minimum coil diameter of said spring is reached, each coil of said minimum diameter forming a neck portion extending coaxially with said central coil, each of said next portions terminating in a coil of said wire defining a knob having a diameter increasing from that of said minimum diameter, and adjacent turns of all portions of said spring being substantially in contact with each other when said spring is in relaxed condition. 